The present invention relates generally to a method for making a vulcanized elastomer capable of combining with Polyurethane without the use of an adhesive, and a method of using the elastomer so made.
The rubber material and the PU (Polyurethane) material are widely used in the footwear industry in view of the fact that the rubber material has an excellent wear-resistant property, which may be as high as 6000 or more in terms of NBS. However, the footwear made of the rubber material is relatively heavy, about 1.0 g/c.c. or more. On the other hand, the footwear made of the PU material, such as the polyester or polyester material, is relatively resilient, resistant to pressure and light in weight, with specific gravity being in the range of 0.3-0.6 g/c.c. However, the footwear made of Polyurethane is less resistant to wear, about 100 or less in terms of NBS.
In view of the advantages of the rubber material and the PU material, it has been suggested that the sole and the heel of a footwear are made of the rubber material, and that the rest of the footwear is made of the PU material. However, such a combination as described above is not technically feasible in view of the fact that the rubber material and the PU material are different from each other in functional base. There is an expensive way to combine the product of the rubber material with the product of the PU material. The surfaces of the product of the rubber material are first roughened and then cleansed with a solvent before applying a surface active agent to the surfaces. The treated surfaces are then coated with adhesive and must be filled with the PU material within three of four days after the surfaces have been coated with adhesive, so as to avoid a failure resulting from the reduction in the surface activity of the treated surfaces.
The prior art method described above is generally defective in design in that the rubber material and the PU material of the product are vulnerable to split, especially under the circumstance that the treatment is not carried out with precision. Moreover, the solvent or adhesive used in the prior art method may be hazardous to the health of workers. In addition, the test results show that the extent to which the product made by the prior art method is resistant to split is only about 2.5-3.0 kg/cm2. By taking all aspects of the prior art method into consideration, it is readily apparent that the prior art method is neither cost-effective nor competitive.
It is therefore the primary objective of the present invention to provide a pollution-free method for making a vulcanized elastomer capable of combing with Polyurethane without the use of an adhesive.
It is another objective of the present invention to provide an improved method for making a vulcanized elastomer capable of combining with Polyurethane to form a product without resorting to an adhesive. The product so made is relatively less vulnerable to split as compared with the product made by the prior art method.
It is still another objective of the present invention to provide a flexible method for making a vulcanized elastomer which can be set aside for a period longer than the period (3 or 4 days) required by the prior art method before the elastomer is combined with Polyurethane without using an adhesive.
It is still another objective of the present invention to provide a cost-effective method for making a vulcanized elastomer capable of being combined with Polyurethane without the use of an adhesive.
In keeping with the principle of the present invention, the foregoing objective of the present invention are attained by a method for making a vulcanized elastomer which can be combined with Polyurethane to form a product without the use of an adhesive. The method comprises a first step in which a mixture is formed by mixing in a mixer a vulcanizable elastomer, a filling agent, an active agent, an aging resistant agent, and a process aiding agent. The mixing process is carried out at a temperature ranging between 150xc2x0 C. and 160xc2x0 C. for less than five minutes. The flakes made of the mixture are kept in an airtight chamber containing the nitrogen gas and having a temperature ranging between 15xc2x0 C. and 20xc2x0 C. for at least 24 hours for stabilizing the physical properties of the flakes. The stabilized flakes are transferred to a mixer in which the vulcanization is carried out in the presence of a vulcanization promoting agent. The vulcanized flakes are removed from the mixer and are then arranged in a molding tool to take form at a temperature ranging between 150xc2x0 C. and 160xc2x0 C. for 5-6 minutes. The elastomer formed in the molding tool is removed from the molding tool and is then soaked in a solution containing water and 10-15% of a non-ionic interfacial agent for 4-5 minutes to bring about the degreasing of the elastomer. The degreasing is carried out in the solution having a temperature ranging between 70xc2x0 C. and 85xc2x0 C. The degreased elastomer is then rinsed for 1-3 minutes with an aqueous solution containing sodium hypochlorite which contains 6-10% of xe2x80x9ceffective chlorinexe2x80x9d. Upon completion of the washing of the elastomer, the elastomer is dried by baking. The dry elastomer is coated with the acetoacetate solution containing 1-3% of chloro cyanuric acid before the elastomer is dried again by baking. The dry elastomer is then allowed to sit without disturbance in a dustproof environment for 48 hours before the elastomer is combined with Polyurethane.
The foregoing objective, features, functions, and advantages of the present invention will be more readily understood upon a thoughtful deliberation of the following detailed description of an embodiment of the present invention in conjunction with the accompanying drawings.